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3 Tools for Spotting Assumptions

3 Tools for Spotting Assumptions

Most Critical Reasoning questions revolve around assumptions. Whether you’re weakening an argument, strengthening an argument, evaluating an argument, or explicitly identifying the assumption in an argument, assumptions are going to be front and center. Thus, spotting assumptions in arguments is one of the key skills for success on Critical Reasoning questions. This article will look at three tools to help you become an ace at doing that.

1) A Critical Mindset

The first important tool you want to bring to every Critical Reasoning question is a critical mindset. That means that you approach each argument looking for flaws. This is very different from how we tend to approach arguments in day-to-day life. When we read or hear an argument in ordinary circumstances we don’t tend to probe it too deeply, or think very critically about it. Unless an argument is so bad as to be almost absurd on its face, we generally accept what we’re told. On the GMAT you need to think of every argument as a flawed argument, and you need to immediately start looking for weaknesses. (Assumptions and flaws can be thought of interchangeably here, because any assumption is a potential flaw in a argument. If the assumption isn’t true, the argument falls apart.) You’ll find that  starting from a position of “This argument is flawed, and I don’t accept the conclusion” makes it much easier to see the assumptions the author is making. Something that is true across the GMAT is that it’s hard to reliably see things unless you’re specifically looking for them. You won’t just “notice” flaws and assumptions — you have to be seeking them out deliberately. So be skeptical of every argument. Ask yourself what else has to be true in order for the argument to work.

2) Looking for Shifts in Language

One of the most reliable ways to find assumptions is to look for shifts in language between the premises and conclusion of an argument. When new stuff appears in the conclusion that wasn’t discussed in the premises, it usually got there by way of an assumption. Let’s look at a simple argument:

Spinach dip has more fiber per tablespoon than does artichoke dip. Therefore, spinach dip is a healthier snack than artichoke dip.

On its face this doesn’t seem like a terribly bad argument. It doesn’t seem wildly implausible. The reasoning isn’t obviously fallacious. But let’s look more closely for a shift in language. The premise of the argument is the first sentence, and the conclusion is the second sentence. The premise says that spinach dip has more fiber than artichoke dip. But the conclusion doesn’t say that spinach dip is a more fiber-rich snack than artichoke dip, it says that it’s a healthier snack. That shift in language from fiber to health is exactly what you need to train yourself to look for. The argument is assuming that having more fiber automatically makes something healthier, but that’s not necessarily true. There could be other differences between the two dips (calories, cholesterol, fat, etc.) that tell a different story. Watching for shifts in language is one of the best ways to find assumptions.

3) Looking for the Most Common Argument Types

Some types of arguments show up again and again on the GMAT. Three you can count on seeing are causal arguments, sampling arguments, and analogy arguments. If you keep an eye out for them, you’ll see them, and when you do you’ll already know what assumptions to look for.

A causal argument claims that one thing is the cause or explanation of something else.

The Blaylock school expanded their computer lab last year and this year’s test scores are up. If we want to increase test scores at our school, we should also expand our computer lab.

The fundamental assumption of any causal argument is that there is no other cause. (There are a few other minor assumptions but that’s the big one.) The previous argument is assuming that the expansion of the computer lab is the only explanation for increased test scores.

A sampling argument argues that because something is true of a sample of things, that same thing will be true about the larger group.

Everyone I’ve talked to has raved about the movie “Justice Delayed.” It will surely be loved throughout the country.

The fundamental assumption of any sampling argument is that the sample is representative. The argument above is assuming that everyone I’ve talked to is a representative sample of the country’s population.

Lastly, an analogy argument makes a comparison between two things and claims that because something is true of the first thing, it will also be true of the second thing.

Justin already has his pilot’s license for small planes. It will be easy for him to learn to fly a helicopter.

The fundamental assumption of any analogy argument is that the two things are similar. The argument above is assuming that flying a plane is similar enough to flying a helicopter that being able to do the former will make the latter easy.

If you approach arguments with a critical mindset, look for shifts in language, and look for common argument types, you’ll have much more success finding assumptions in Critical Reasoning questions.

Read Next : Causality Arguments: GMAT Critical Reasoning



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